by Michael Brinsden

When our Mopars get to a certain age the vehicle body, rubbers and general sealing against dust, water and fumes deteriorates. To keep your vehicle in top condition it may become necessary to check the sealing used in the vehicle construction. This article explains the checking and maintenance actions that can be conducted from time to time to ensure that the vehicle does not deteriorate any further and that the vehicle continues to remain your pride and joy.

1.0 Tools and Sealing procedures

Before starting on a check of the body seals it is handy to have ready the following items-:

a) Roll of masking tape

b) Tin of trace powder

c) Tube of weatherstrip adhesive

d) Puffer syringe

e) Carpenters chalk

f) Wooden or plastic trim stick

g) Tube of neutral caulking compound

h) About 750mm of small diameter hose

And, as you may need it, a roll of closed cell foam with adhesive applied to one side.

A vehicle body contains many openings in the body metal. These are a necessary feature of the original manufacturing method with, in some cases, holes left for access during vehicle assembly. For example there are many metal lap joints in the vehicle construction and with time the original sealer hardens and cracks. These can be resealed by scraping the old sealer off, washing the joint to remove road grime, drying and then resealing with the caulking compound. Make sure that the sealer is applied to cover both pieces of metal in the lap joint. Use a similar procedure for those seals on joints using three sheets of metal.

For those openings in the body, for which you do not have a plastic or rubber grommet, fill the hole with sealer, force the sealer through the hole, and finger spread the sealer such that it overlaps the metal right around the hole diameter. Do this on both sides of the hole if possible. If access to the other side of the hole is impossible then roll up a small section of newspaper, carefully stuff it into the hole and depress the newspaper around the hole diameter with a screwdriver. Apply the sealer making sure that the sealer completely fills the depressed area on the newspaper and then finger spread to cover the metal as before.

It is worth noting that when your vehicle is in motion its passage through the air creates a vacuum on the exterior and along the side and rear glass. With the vents open, or the heater or air conditioning operating, the interior of the vehicle is pressurised. This causes air to flow from the interior of the vehicle, where an opening exists, which can cause an annoying air whistle or growl, particularly at high speed.

2.0 Water and Dust Leak Testing

2.1 Preliminary Inspection

Before conducting any tests inspect the general area where the water or dust is getting into the vehicle. Check for things that are obvious such as broken or damaged weatherstrips, gaps or holes at body joints or corners, or loose grommets and cracked seals. Traces of rust along a body seam are a sign of an open joint even though the opening is not visible. Partial sealing compound adhesion or air holes in the sealing material at body seams can also account for some leaks.

It is a good idea to check the door opening surfaces especially after driving in the rain. Look at the dried road grime outside the weatherstrip contact line. If the weatherstrip is sealing properly then no road grime should be visible on the inside of the contact line.

2.2 Door Alignment

When inspecting the vehicle check that the doors fit properly into the door openings in the body. If the doors are not aligned properly, or the door striker is not correctly positioned, the weatherstrip may not be able to make a good seal. When the doors are set correctly the weatherstrip compresses along its whole length when the door is fully closed. This compression allows the weatherstrip edge to make a firm even contact around the door opening to provide a good seal without being crushed. Don’t try to compensate for poor door alignment by moving the door striker inward. This will cause the weatherstrip to bottom out, and with repeated crushing, will cause the strip to lose its resilience and eventually break down.

As for the doors check that the boot weatherstrip is operating properly, especially after the vehicle has undergone body repairs.

3.0 Water Leak Test

This practical test is easy to implement and provides the only method to guarantee the effectiveness of repairs around the windshield, rear window, boot, and inner door watershields and at body seams and joints.

3.1 Hose Adjustment

To test for leaks it is best to use a small stream of water. Too much pressure can cause water to force past a good sealing weatherstrip or it will wet a wide area and cause difficulty in identifying the leak point. Adjust the hose pressure to obtain about 75mm of water projection from the hose end.

3.2 Windshield and Rear Window

Commence at the lower corners and move the water stream slowly up the sides and across the top of the glass. Note when the leak occurs and seal the rubber to glass, and rubber to body flange, in the leaking area with the neutral weatherstrip sealing compound.

3.3 Doors

Seat a friend in the vehicle to watch for water ingression as the hose is worked around the gap at the door edge on the vehicle exterior. Start the check at the lower edge of the door and work upward. If the weatherstrip is not sealing properly it is easy to see where the water leaks into the vehicle interior. Mark each position detected with chalk so that they can be found when the door is open. It is best to fix the lower leaks found before testing at the top of the door.

If the test shows the weatherstrip is sealing correctly, run water along the side glass at the belt line weatherstrips and check the inside door trim panels for dampness, especially at the bottom. If the panels are wet then the plastic shield, mounted on the inner door frame with tacky adhesive, is leaking and it should be repaired or replaced. It is best to ensure that the bottom portion of this plastic shield is tucked into the slots in the door panel when remounted. This will direct water to the inside of the door and prevent leakage to the vehicle interior. Lastly check that the drain holes at the bottom of the door are free of dirt and road grime. If you have rubber grommets mounted on these drain holes ensure that the flap is free to move and allows water to drain onto the vehicle sills.

Note: After this test, and the correction of any faults, allow the doors to thoroughly dry, clean out any rubbish or dirt from the door interior, and apply fish oil to the inner parts of the door making sure that the fish oil does not make contact with the door glass. Remove any rubber grommets in the door drain holes before the application of the fish oil. Allow the fish oil to dry (about three weeks) and then reinsert the drain hole grommets.

Dry Test Method

An alternative dry method of checking door weathershields is to use carpenter’s chalk. Open the door and rub the chalk on the sealing surface of the weathershield. Use white chalk for dark body colours and blue chalk for light body colours. With the chalk applied close the door and then reopen it. The chalk should transfer to the body surface contacted by the weathershield in a continuous unbroken line if the seal is satisfactory.

If it is difficult to get a good chalk transfer to the body coat the body with a thin film of body wax where it is contacted by the weatherstrip. The wax will retain the chalk from the weathershield and leave a distinct imprint.

Where gaps of 25mm or more appear in the weatherstrip seal build up the weatherstrip by glueing cut lengths of flat pliable rubber under the strip. Where low points are found at body joints, or other places around the seal, it will be necessary to build up these points with body filler and then sand and paint. Likewise high spots must be sanded back and painted.

Note: If carpenter’s chalk is not available blow trace powder with the syringe around the weathershield with the door closed. If the powder leaves an unbroken line around the outside of the weatherstrip then the seal is good. If the test shows powder on the inside of the weatherstrip, or on its contacting surface, the strip is not sealing properly at these points. Clean up the powder after this test.

3.4 Boot

Check that the boot lid is flush with the surrounding metal of the vehicles exterior. Open the boot and examine the weatherstrip flange for distortion or damage. Inspect the weatherstrip for splits or separation from the mounting surface and correct if necessary. With the hose run water over the gap between the boot lid and the vehicle body, once again starting at the top near the rear window. If the seams, or pin holes, are the cause of the leak repair with the caulking compound, allow to dry and finish with the vehicle touch up paint.

If the weatherstrip is the cause of the leak then try adjusting the boot lid, for tighter compression of the weatherstrip, by adjusting the mounting nuts on the boot lid hinges. Note that this will depress the boot lid with respect to the adjacent panels and detract from the vehicle appearance. It is better to install a new boot weatherstrip which is available today from various suppliers.

If a dry test is preferred then use the same powder method as described for the door weathershield.

If these tests do not find the leak then test the rear window rubber– the most common leak for water in the boot.

3.5 Tail Lights

With the boot open test with a water stream applied to the tail light. Watch inside the boot for ingression of water through the bulb holder body or the tail light cut out seal. If leakage is found around the cut out seal repair with the closed cell foam. Make sure that there is no water in the tail light assembly.

If water has entered the boot, remove the grommets in the inner quarter panel, and allow the boot to thoroughly dry. Then apply fish oil to all of the metal surfaces of the boot interior. This is particularly important for the cavity between the boot floor and the rear quarter panel. Replace the grommets in the inner quarter panel to prevent water ingression in wet driving conditions.

3.6 Front Cowl

Direct the water hose flow through the cowl air inlet grill with the hose outlet facing the rear of the vehicle. If no leak is found raise the bonnet and direct water over the body seams on the firewall and engine bay area. Make sure that the radio antenna lead-in grommet is in place and check all body seams hidden by the front fenders. You may have to remove the inside trim panels (kickboards) to see where the water is leaking into the interior.

3.7 Floor Pan

Usually water that leaks from higher up in the vehicle ends up on the floor pan soaking the underfelt and the carpet. If leaks from other sources have been eliminated by adopting the procedures enumerated above then the only remaining source of the water leak is from below through the floor pan body joints or grommets.

As a first step remove the door sill trim, seats and the centre consol to give a clear field for inspection. Remove the carpet and underfelt but note the location of the damp area. Check the body seals and floor pan grommets in that area. Traces of road grime or mud can indicate a leaky area as can rust signs along the body joints. Clean off any old sealant and rust, wash, dry and then reseal the body joint edges and grommet areas that are suspected. Allow the sealant to dry and then paint the affected area with fish oil. The repair work can be tested by driving the vehicle in wet conditions. Do not replace the underfelt and carpet until the fish oil has reached touch dry (about three weeks).

Note: When repairing leaks in the floor pan take great care with the resealing operation as pin holes in the sealant can undermine your good work and, over time, lead to further leaks of water and dust.

4.0 Wind Noise Leak Testing

Leaks which cause wind noise inside the vehicle do not cause the damage or mess possible with water and dust leaks. However the noises made by air leaks can be very irritating especially on long haul road trips. Most wind noises are caused by air leaking out of the vehicle and with the cowl vents open, or the heater or air conditioner operating, the forward motion of the vehicle causes the air pressure to rise in the vehicle interior. This is especially so at high vehicle speeds and the air pressure differential, between the interior and exterior of the vehicle, causes air to leak through every available orifice.

4.1 Road Test

As before check weatherstrip condition, door and glass alignment and any poorly fitting mouldings or trim. Retract the radio antenna and close all doors and windows correctly. Turn off the radio and heater/air conditioner blowers and move the heater controls to the vent position. Choose a quiet low traffic environment where the vehicle can be driven at cruising speed.

Commence the test run with the fresh air Inlet Vents in the closed position. If the irritating noise is present then the likely cause is air coming into the vehicle and the noise will be loudest on the windiest side. An air draft can usually be felt if the leak is large. Mask off the suspected area with masking tape to see if this corrects the problem.

Open the fresh air Inlet Vents. If the noise disappears then the air intake leak is confirmed.

If the noise can only be heard when the fresh air Inlet Vents are open then the sound is probably caused by air leaking from the inside to the outside of the vehicle. The sound should change in pitch or volume as the vehicle speed varies. To locate the leak use a friend to listen through the small diameter flexible hose around the door seals and windows for the location of the loudest noise.